Add support for disabled check actions

Also moves <gr-checks-action> into its own file.
Also makes actions functional on the hovercard (needs eventTarget prop).
Also adds proper action callbacks to fake actions.

Change-Id: I6cbd66e1dd363c7aef855681513168fe7fcb09a0
diff --git a/polygerrit-ui/app/services/checks/checks-util.ts b/polygerrit-ui/app/services/checks/checks-util.ts
index 0a0881b..7eb2a5d 100644
--- a/polygerrit-ui/app/services/checks/checks-util.ts
+++ b/polygerrit-ui/app/services/checks/checks-util.ts
@@ -130,7 +130,7 @@
 
 export function primaryRunAction(run: CheckRun): Action | undefined {
   return runActions(run).filter(
-    action => action.name === primaryActionName(run.status)
+    action => !action.disabled && action.name === primaryActionName(run.status)
   )[0];
 }